The present invention relates to exercise devices and in particular to exercise cycles generally utilized for aerobic exercise and cardiovascular stimulation wherein for operation an exerciser pedals the device in a manner similar to a bicycle.
Conventional exercise cycles are generally intended to simulate bicycle riding. For operation of the devices, an exerciser generally sits astride the device and rotates a pedal axle by means of pedals such as bicycle pedals. Exercise is received by the operator, since energy is required for the pedaling action.
Conventional exercise cycles are generally of two basic types: in the first, the pedal action communicates with a wheel by mechanical means such as a chain. As the pedal axle is rotated by pedaling action of the exerciser, the wheel is rotated. Resistance to rotation of the wheel is generally provided by an adjustable mechanical device causing a friction brake to engage a surface of the wheel. As resistance to rotation of the wheel is increased, more energy is required to pedal the axle and the exerciser receives a greater workout. Unlike a bicycle, the rotating wheel is generally suspended out of ground contact, so that the device remains stationary while being used.
Such conventional devices generally suffer from two interrelated problems. First, they do not simulate bicycle riding well and secondly, they are often uncomfortable for the user. The reasons for these problems are understandable by reference to conventional bicycle riding.
In a conventional bicycle, as with conventional exercise cycles, the pedals are mounted upon pedal arms which are oriented 180.degree. out-of-phase with one another. Thus, whenever the right pedal arm is at its maximum upward extension, the left pedal arm is at its maximum downward extension. In a typical pedaling cycle, a pedal arm begins at 0.degree., that is extending straight upward, rotates to 90.degree., that is extending toward the front part of the bicycle, continues to rotate through 180.degree., that is bottom dead center, through 270.degree. and back to 0.degree.; or through a 360.degree. arc. The opposite pedal being 180.degree. out-of-phase, begins at 180.degree. rotates through 270.degree., 0.degree., 90.degree. and back to 270.degree..
It is readily seen that for the conventional bicycle, maximum rotative force can be more readily applied to a pedal, mounted on a pedal arm, when the pedal arm is located at the 90.degree. position, that is extending forwardly. If the sum of the two pedal arms is considered, the amount of torque which may be easily applied by a rider is at a maximum when the pedal arms are horizontal and at a minimum when the pedal arms are vertical. This results from a general location of the bicycle seat vertically above the pedal axle.
One of the reasons bicycle riding is relatively comfortable is because the shape of the human body and the capabilities of human leg muscles generally correspond to the same pattern as the above torque pattern for pedaling. That is, the human bicycle rider generally finds that his or her legs are more capable of providing torque, or imparting power to the pedals, when the pedal arms are substantially horizontal.
As a human rides a bicycle, the amount of power transmitted to the wheel, through the pedaling action, increases and decreases on a periodic cycle. Generally, the amount of power is at a maximum when the pedal arms are in a horizontal position and at a minimum when the pedal arms are generally vertical. The rider feels a smooth pedaling action for the reason that this generally sinusoidal periodicity somewhat matches muscle capability, and also because the forward momentum of the bicycle generally carries the pedaler through top and bottom dead center without the need for much work.
In conventional exercise cycles of the first described type, since the cycle is stationary, there is no forward momentum to help carry the pedaler through top and bottom dead center. Since the amount of friction provided by the brake is constant, at any given point in the pedaling cycle the same amount of energy is required to rotate the wheel at a constant speed. Since it is easier to impart power to the pedals when the pedal arms are horizontal, the exerciser generally finds it easier to pedal when the pedals are horizontal and harder to pedal when the pedal arms are vertical. Thus, a smooth, comfortable pedaling action is not obtained, and it is hard to maintain a constant pedaling speed.
A second type of conventional exercise cycle has been developed to overcome some of these problems. In these cycles, the wheel which is rotated by action of the pedal axle is very heavy and acts as a fly wheel to carry the pedals through top and bottom dead center. Thus, if the pedaler relaxes somewhat at top and bottom dead center, that is when the pedal arms extend vertically, the momentum of the wheel will carry the pedal arms through the vertical position toward the horizontal, where pedaling is easier. A problem with the second type of conventional exercise cycle is that the fly wheels can take up considerable space, may be relatively heavy, and may be relatively expensive to manufacture. Further, the exerciser may encounter pedaling discomfort when the rotational speed of the heavy fly wheel is being increased or decreased.